Self-extinguishing plastics compositions

ABSTRACT

SELF-EXTINGUISHING STYRENE POLYMERS CONTAINING (A) AN ORGANIC BROMINE COMPOUND AND LEAD NAPHTHENATE OR (B) AN ORGANIC CHLORINE COMPOUND AND IRON NAPHTHENATE. THE COMBINATIONS (A) AND (B) ARE EXCEEDINGLY EFFECTIVE WHEN USED AS FLAME-PROOFING AGENTS.

3,505,815 Patented July 27, 1971 US. (Cl. 260-25 4 Claims ABSTRACT OFTHE DISCLOSURE Self-extinguishing styrene polymers containing (a) anorganic bromine compound and lead naphthenate or (b) an organic chlorinecompound and iron naphthenate. The combinations (a) and (b) areexceedingly effective when used as flame-proofing agents.

This application is a continuation-in-part of application Ser. No.437,302, filed Mar. 4, 1965, and now abandoned.

This invention relates to self-extinguishing plastics compositions andmore particularly to plastics compositions which contain a styrenepolymer, an organic bromine compound and lead naphthenate or an organicchlorine compound and iron naphthenate.

It is known that halogen-containing substances may be used as flameretardants for thermoplastic polymers. To

achieve adequate flameproofing it is necessary to add relatively largeamounts of halogen-containing substances to the polymers. Many of theproperties of the polymers are, however, detrimentally aiTected in thisway.

It is also known that the flame-retarding action of halogen-containingcompounds may be enhanced by additives so that an adequate effect can beachieved with considerably smaller amounts of these substances. Thus itis possible to improve the flameproofing effect of organic brominecompounds by adding organic peroxides. Organic peroxides have thedisadvantage that they are toxic and in some cases readily decomposeexplosively. Personnel with sensitive skins who handle such peroxidesmay contract dermatitis. Moreover, expensive and troublesome precautionsmust be taken in handling peroxides to avoid explosions. It is alsoknown that peroxides slowly decompose even at room temperature so thatstored products are no longer self-extinguishing. Moreover, it is alsoalready known that chlorinated hydrocarbons may be used with antimonytrioxide as fiameproofing agents for thermoplastic polymers. It is adisadvantage that a relatively large amount of antimony trioxide isrequired so that the mechanical properties are deleteriously affected.Moreover, this substance cannot be added to the monomers in some methodsof polymerization, for example bead polymerization, because it is nothomogeneously distributed in the polymer.

We have now found that self-extinguishing plastics compositions do nothave the said disadvantages when they contain:

(A) a styrene polymer,

(B) an organic chlorine or bromine compound as a fiameproofing agent,and

(C) lead naphthenate where an organic bromine compound is used or ironnaphthenate where an organic chlorine compound is used.

Styrene polymers (A) which are included within the scope of theinvention are polystyrene and copolymers of styrene which contain atleast 50% by weight of styrene units. Examples of copolymerizationcomponents are acrylonitrile, methacrylonitrile, esters of acrylic acidor methacrylic acid with alcohols having one to eight carbon atoms,fumaric esters of alcohols having one to eight carbon atoms, N-vinylcompounds, such as vinylcarbazole, vinylidene chloride, butadiene oralso small amounts, for example, 0.5 to 0.01% by weight, ofdivinylbenzene.

Organic chlorine or bromine compounds (B) suitable as fiarneproofingagents should advantageously contain from 40 to by weight of chlorine orbromine and at least four carbon atoms and should advantageously have ahigh melting point. The chlorine or bromine atoms in the chlorine orbromine compounds are preferably attached to aliphatic or cycloaliphaticcarbon chains. Examples of suitable organic bromine compounds are:tetrabromobutane, dibromoethylbenzene, dibromopropanol or esters oracetals of dibromopropanol such as tris-(dibromopropyl) phosphate, andalso pentabromodiphenyl ether. Organic compounds which are of lowvolatility, which exert little or no plasticizing action and which donot have an unpleasant odor are particularly suitable. These includeparticularly the bromination products of butadiene or isoprene oligomersor polymers, for example, 1,2,5,6,9,10-hexabromocyclododecane,octabromohexadecane or brominated natural or synthetic rubber. Thebromine compounds are used in amounts such that the plasticscompositions have a bromine content of at least 0.5% by weight. In mostcases it is not necessary for the compositions to contain more than 5%by weight of bromine. The compositions advantageously contain from 1 to3% by weight of bromine.

Examples of suitable organic chlorine compounds are low molecular weightchlorine compounds, such as hexachlorocyclododecane,hexachlorocyclopentadiene, hexachloroendomethylenetetrahydrophthalicacid, tetrachlorobutyrolactone and tetrachlorobutanediol diacetate. Highmolecular weight chlorine-containing compounds which have little or noeffect on the properties of the styrene polymers are particularlysuitable. Examples of these compounds are polyvinyl chloride,afterchlorinated polyvinyl chloride or polyvinylidene cholride whichhave a chlorine content of from 56.8 to 73.2% by weight and chlorinatedpolyisobutylene having a chlorine content of about 40 to 50% by weight.Chlorinated parafiins having a chlorine content of 60 to 75 by weightwhose carbon chain contains at least eighteen to forty carbon atoms arealso particularly suitable. In all cases it is expedient to use chlorinecompounds having a high chlorine content in order to keep the amountthereof in the plastics composition to a minimum. The chlorine compoundsare added to the plastics compositions in such amounts that the latterhave a chlorine content of at least 2% by weight. In most cases it isnot necessary for the compositions to contain more than 7% by weight ofchlorine. The compositions preferably contain from 3 to 6% by weight ofchlorine.

Tht amount of lead naphthenate or iron naphthenate contained in theplastics compositions can vary from about 0.01 to 5% by Weight based onthe weight of the compo sition, and preferably is from 0.1 to 2% byweight.

The plastics composition may be processed into selfextinguishingmoldings or profiles, for example, by injection molding or extrusion.When dissolved in organic solvents, the plastics compositions are alsosuitable as flameretardant lacquers, for example, for painting *WOOd ormetals. By reason of their relatively low content of organic halogencompounds, the molding materials according to this invention havesoftening points which diifer only slightly from those of the polymerscontained therein.

Plastics compositions which are suitable for the production ofself-extinguishing expandable materials have particular importance.These contain an expanding agent (D). Expanding agents (D) are definedas normally gaseous or liquid hydrocarbons or halohydrocarbons orsubstances which disengage gaseous substances at a given temperature.Aliphatic hydrocarbons and chlorofluorohydrocarbons Whose boiling pointsare below the softening point of the polymer, preferably from l to +50C., and which do not dissolve the polymer, are particularly suitable.The expanding agent may be present in the expandable plasticscompositions in amounts of 2 to 20%, preferably 3 to by weight withreference to the plastics composition. Self-extinguishing expandedplastics moldings may be prepared from the said expandable plasticscompositions by heating fine particles of these compositions ingas-permeable molds to temperatures above the softening point of thepolymer contained in the composition so that the particles expand andfuse together to form moldings. These expandable plastics compositionsmay also be processed into foam sheeting by means of extruders.

Other components may be contained in the plastics compositions, forexample, fillers, color pigments, lubricants, plasticizers, antistatics,antiagers or stabilizers.

For the production of the plastics compositions, the lead naphthenate oriron naphthenate may be mixed together or successively with the styrenepolymer and if desired with other components. For example, they may beincorporated into the plastics on rollers, in extruders or in kneaders.In many cases they may be added to the monomers prior to polymerization.It is also possible, for example, in the production of cast films andsheeting, to add the metal salt of the organic acid and the halogencompound to a solution of the plastic and then to evaporate the solvent.

weight; the K-values are determined by the method of H. Fikentscher,Cellulosechemie, 13 (1932), page 60.

EXAMPLE 1 TABLE 1 Extinction time of the film Metal salt Parts Halogencompound Parts (seconds) Iron naphthe- 0.06 Chloroparafiin (Cl=70%). 1.65.

nate. o 1.6 Burns on. Lead 0.1 Hexabromocyclododeeane. 0.4 3.

naphthenate. o 0.6 20.

EXAMPLE 2 0.1 part of azodiisobutyronitrile, one of the metal saltsgiven in Table 2 and one of the halogen compounds are dissolved in 20parts of styrene. The mixtures are heated for four hours at 70 0., threehours at 100 C., and three hours at 150 C. The polymers obtained arethen dissolved in 60 parts of methylene chloride. Three (3) parts ofpentane is added to the solutions from which expanded films are preparedas described in Example 1. These are tested as described above.

TABLE 2 Extinction time of the Metal salt Parts Halogen compound PartsK-value fllm(seconds) 0.05 Hexabrornocyclododecane- 0.4 43. 7 5. Leadnaphthenate" 0.1 .do 0.4 43.3 3.

do. 0.4 39.8 Burns on.

0.4 Chloroparatflu (0l=70%)- 1.6 26.6 Zero. Iron naphthenate... d {'85%? 3 1. 6 35. 4 Burns on.

EXAMPLE 3 The fact that the lead naphthenate or iron naphthenate doesnot disturb the polymerization is a particular advantage. Some of thecompounds activate decomposition of the peroxide catalysts. The monomersmay, therefore, be polymerized in the presence of the metal salts and ofthe organic halogen compounds for the production of theselfextinguishing plastics compositions according to this invention. Inthis way a particularly homogeneous dispersion of the flameproofingagents and the metal salts in the composition takes place. Sometimes thepolymerization of the monomers may be carried out at substantially lowertemperatures than in the absence of the salts.

The self-extinguishing properties of the molding materials are tested inthe following way: to test unexpanded plastics compositions, moldingshaving the dimensions 0.1 x 3 x 12 cm., and to test expanded plasticscompositions, moldings having the dimensions 3 x 3 x 12 cm. are held forfive seconds in the nonluminous flame of a bunsen burner and thenremoved from the flame with a gentle movement. The time taken by themolding to become selfextinguished after removal from the flame is ameasure of its flame retardancy. An extinction period of 0 to 2 secondsis regarded as very good and one of 2 to 5 seconds as good. Extinctiontimes of less than ten seconds are fegarded as adequate. Moldingmaterials that have an insufiicient self-extinguishing finish or none atall will burn completely after removal from the flame.

The following examples will further illustrate this invention. The partsspecified in the examples are parts by 1940 parts of styrene mixed with40 parts of hexabromocyclododecane, 200 parts of petroleum ether, 8.8parts of azodiisobutyronitrile and 20 parts of lead naphthenate aresuspended in 4000 parts of water containing 4 parts of polyvinylpyrrolidone having a K-value of dissolved therein are heated in astirred autoclave for thirty hours at 70 C. The polymer in the resultantbead plastics composition has a K-value of 67.0

The bead composition is expanded with steam to a bulk density of 20g./l. After the expanded composition has been kept for twenty-fourhours, it is heated in a gaspermeable mold with superheated steam sothat the particles expand further and fuse together to form a molding. Amolding tested by the above method is self-extinguished eight secondsafter having been removed from the flame.

Foam articles prepared from a composition containing no leadnaphthenate, but otherwise containing the same components, continue toburn when removed from the extraneous flame.

EXAMPLE 4 The extreme effectiveness of either (a) an organic brominecompound and lead naphthenate, or (b) an organic chlorine compound andiron naphthenate is demonstrated in the subject example. Theself-extinguishing properties of molded compositions consisting ofpolystyrene containing the subject combinations of flame-retardingagents is demonstrated from the experimental results set forth below.The test was carried out in the manner described above.

Chloroparafiin Extinction time Fe-naphthenate [percent] [percent] [sec.]

SbGhacetylacetonate [percent] Pb-naphthenate [percent]Hexabromocyclododecane [percent].

Sb O14- acetylacetonate [percent] Pb-naphthenate [percent]Ohloroparaffin [70% 01] [percent].

We claim:

1. A self-extinguishing plastics composition comprising (A) a styrenepolymer selected from the group consisting of polystyrene and copolymersof styrene and a monomer selected from the group consisting ofacrylonitrile, methacrylonitrile, esters of acrylic and methacrylic acidwith alcohols having one to eight carbon atoms, fumaric esters ofalcohols having one to eight carbon atoms, vinylcarbazole, vinylidenechloride, butadiene, divinylbenzene and mixtures thereof, said styrenepolymer containing at least 50% by weight of styrene units,

(B) 0.5-5% by Weight of an organic bromo compound selected from thegroup consisting of tetrabromobutane, dibromoethylbenzene, esters andacetals of dibromopropanol, pentabromodiphenyl ether, brominationproduct of butadiene and isoprene oligomers and polymers, brominatednatural rubber, said brominated compounds containing between 40 and 75%by weight of bromine, and

(C) 0.01 to 5% by weight, with reference to said composition, of leadnaphthenate.

2. A self-extinguishing plastics composition comprising (A) a styrenepolymer selected from the group consisting of polystyrene and copolymersof styrene and a monomer selected from the group consisting ofacrylonitrile, methacrylonitrile, esters of acrylic and methacrylic acidwith alcohols having one to eight carbon atoms, fumaric esters ofalcohols having one to eight carbon atoms, vinylcarbazole, vinylidenechloride, butadiene, divinylbenzene and mixtures thereof, said styrenepolymer containing at least by Weight of styrene units,

(B) 2 to 7% of a chlorinated organic compound selected from the groupconsisting of hexachlorocyclododecane, hexachlorocyclopentadiene,hexachloroendomethylenetetrahydrophthalic acid,tetrachlorobutyrolactone, tetrachlorobutanedioldiacetate, polyvinylchloride, chlorinated polyvinyl chloride, polyvinylidene chloride,chlorinated polyisobutylene, chlorinated paraffins, said chlorinatedcompounds containing between 40 and by weight of chlorine, and

(C) 0.01 to 5% by weight, with reference to said composition, of ironnaphthenate.

3. A self-extinguishing plastics composition as claimed in claim 1 whichcontains 2 to 20% by weight, with reference to said composition, of anexpanding agent selected from the group consisting of aliphatichydrocarbons, chlorohydrocarbons and chlorofluorohydrocarbons having aboiling point which is below the softening point of said polymer (A).

4. A self-extinguishing plastics composition as claimed in claim 2 whichcontains 2 to 20% by weight, with reference to said composition, of anexpanding agent selected from the group consisting of aliphatichydrocarbons, chlorohydrocarbons and chlorofiuorohydrocarbons having aboiling point which is below the softening point of said polymer (A).

References Cited UNITED STATES PATENTS 2,636,867 4/1953 Humfeld 26023S2,924,532 2/ 1960 Dereich 260-F.P. Dig. 2,996,528 8/1961 Marks et a1.260--F.P. Dig. 3,031,425 4/ 1962 Schoepfle et a1. 260-F.P. Dig.3,093,599 6/1963 Mueller et a1. 260-F.P. Dig. 3,211,768 10/1965Considine 260F.P. Dig.

MURRAY TILLMAN, Primary Examiner M. F OELAK, Assistant Examiner U.S. C1.X.R. 26045.75, 45.85, 93.5

